DESCRIPTION

These functions allow the manipulation of POSIX signal sets.
sigemptyset() initializes the signal set given by set to empty, with
all signals excluded from the set.
sigfillset() initializes set to full, including all signals.
sigaddset() and sigdelset() add and delete respectively signal signum
from set.
sigismember() tests whether signum is a member of set.
Objects of type sigset_t must be initialized by a call to either
sigemptyset() or sigfillset() before being passed to the functions
sigaddset(), sigdelset() and sigismember() or the additional glibc
functions described below (sigisemptyset(), sigandset(), and
sigorset()). The results are undefined if this is not done.

RETURNVALUE

sigemptyset(), sigfillset(), sigaddset(), and sigdelset() return 0 on
success and -1 on error.
sigismember() returns 1 if signum is a member of set, 0 if signum is
not a member, and -1 on error.

ERRORS

EINVALsig is not a valid signal.

CONFORMINGTO

POSIX.1-2001.

NOTES

GlibcNotes
If the _GNU_SOURCE feature test macro is defined, then <signal.h>
exposes three other functions for manipulating signal sets.
intsigisemptyset(sigset_t*set);
returns 1 if set contains no signals, and 0 otherwise.
intsigorset(sigset_t*dest,sigset_t*left,sigset_t*right);
places the union of the sets left and right in dest.
intsigandset(sigset_t*dest,sigset_t*left,sigset_t*right);
places the intersection of the sets left and right in dest.
sigorset() and sigandset() return 0 on success, and -1 on failure.
These functions are non-standard (a few other systems provide similar
functions) and their use should be avoided in portable applications.